The present invention relates to a passenger ship, such as a passenger liner or a ferry for example.
Such a ship comprises a main structure bounded by a hull and its upper deck (or freeboard deck), above which rises at least one superstructure consisting in particular of an assembly of decks and of longitudinal and transverse bulkheads (partition walls). The superstructures of these ships are subjected to loads generated by the deflection of the ship during its passage through the swell, loads that are manifested by a parabolic bending moment distribution and by a shear load. On large size ships of the passenger liner or ferry type, the type of construction of these superstructures involves said superstructures contributing to the aggregate strength of the ship. Consequently, they are taken into account for the strength calculation of the “hull girder”, that is the girder schematic that represents the set of loads to which the structure of a ship is subjected. However these superstructures are currently made up of decks interconnected by interior bulkheads and/or boundary bulkheads called “platings”, as well as by stanchions.
Depending on the type of construction selected, these interior bulkheads, particularly those oriented in the longitudinal direction of the ship, and these platings, the number of which is high, complicate the structure of ships. This involves not only a complication of the superstructure itself but also of the main structure aimed at ensuring structural continuity, incidentally increasing the overall weight of the superstructure and/or not allowing good natural illumination of the cabins and other passenger living spaces. In particular, in the interior portions of these ships, certain spaces are “blind”, in the sense that they do not get the benefit of any outside lighting.
The present invention aims to resolve these problems. In other words, it has the object of proposing a ship the overall structure whereof is as strong as that of currently known ships, carrying the full set of loads, but allowing the elimination of part of the decks, the interior bulkheads and/or the platings of the superstructures, particularly so as to:                simplify the structure of the ship and thus reduce the cost of its construction;        lighten the weight of the superstructures and thus reduce the consumption of energy by the ship required for its propulsion and make it more stable by lowering its center of gravity;        facilitate the layout of spaces by means of non-structural partitions;        improve the lighting of the spaces.        
Thus, the present invention relates to a passenger ship, such as a passenger liner, which includes a main structure bounded by a hull and its upper deck (or freeboard deck, which is positioned above a waterline defined by a displacement of the hull when the passenger ship is at rest). At least one superstructure rises above the upper deck and is characterized by the fact that it comprises at least one arch which stands generally fore and aft, and which extends at least partly over the main structure, its opposite ends being firmly joined to this main structure, so that the arch carries at least partly the loads connected with its deflection. In other words, said arch begins toward the stern and extends in the direction of the bow.
Thus, the arch aims to limit the deflection (deformation) of the ship when it is on the swell (in this case, the arch is in tension when the middle of the ship is on the crest of a swell, and in compression when the two ends of the ship are on the crest of a swell). This makes it possible to thus limit the bending of the ship, which constitutes an essential criterion in the classification of ships. In the present application, the term “deflection” signifies “deformation”.
Preferably, when the superstructure consists particularly of an assembly of decks and of structural transverse bulkheads, at least part of the decks of the superstructure is fixed to this arch. The arch then also carries a large part of the loads to which the superstructure of the ship is subjected. It is thus possible, in the construction of the superstructures, to eliminate certain longitudinal structural bulkheads and/or some platings which are normally necessary for avoiding or limiting relative slippage of the decks and thus contribute to the aggregate strength of a ship according to the state of the art, particularly for resisting the shear loads thus generated.
This makes it possible, as already indicated above, to:                simplify the structure of ships and thus to reduce their construction cost;        lighten the weight of the superstructures and thus reduce the energy consumption of the ship required for its propulsion, and make it more stable by lowering its center of gravity;        facilitate the layout of spaces by means of non-structural partitions and obtain spaces with greater dimensions;        improve the lighting inside the ship.        
According to other advantageous characteristics:                said arch stands vertically and parallel to its longitudinal axis;        said arch exhibits a discontinuity, i.e. it has an interruption in its middle zone, so that it consists of two curved branches with space between them;        the ship has two arches arranged, symmetrically or not, on either side of its medial longitudinal axis;        said arches extend in immediate proximity to the hull platings;        the distance separating the opposite ends of said arch is substantially equal to the length of said ship;        said arch is supported by stanchions or any equivalent structural means which, like a stanchion, allows the provision of large openings in the surroundings of the superstructures, so as to bring natural light to the interior of the ship;        said arch consists of an assembly of preferably hollow struts;        said arch consists of a mesh;        said arch is made of metal, of composite material, for example based on carbon fibers, or of a combination of different materials;        at least one part of the transverse structural bulkheads is joined to said arch;        said arch is associated with at least one pillar the upper end whereof is joined to said arch, while its base is firmly joined to said main structure.Other characteristics and advantages of the present invention will appear upon reading the detailed description of certain preferred embodiments.        